1. Technical Field
The present invention relates to a flat display module and in particular, relates to the reinforcing structure for a flat display panel with a flexible wiring substrate such as TCP (Tape Carrier Package) and COF (Chip on Film) connected to the display panel.
2. Background Art
A flat display device such as a liquid crystal display device (hereinafter, referred to as an LCD device) is widely used in such fields as the office automation equipment, the audio visual equipment and the portable terminal equipment due to its beneficial feature such as thin type, light-weight and low power consumption. This LCD device includes a liquid crystal display module (hereinafter, referred to as an LCD module) and a backlight module. As is shown in FIG. 7A and FIG. 7B, the LCD module includes a liquid crystal (LC) panel 1, a pair of polarizing plates 2, and a flexible wiring substrate 4 (hereinafter, referred to as a flexible substrate.) The LC panel is composed of two transparent substrates sandwiching liquid crystal therebetween. The polarizing plates 2 are disposed on front and rear surfaces of the LC panel 1. The flexible substrate 4 is provided with a driver IC for driving the LC panel 1.
To make the LCD device thin is a significant issue and thus further thinning of the transparent substrates of the LC panel is desired. In recent years, accordingly, such thin transparent substrates as of no more than 0.5 mm thickness have been used, and more thinner transparent substrates of 0.4 mm or 0.3 mm thickness have been also tried.
By using such thin transparent substrates, a thin LC panel can be realized. However, breakage or crack at a peripheral portion of the transparent substrates tends to occur, in particular, at region adjacent to connecting portion for the flexible substrate due to mechanical pressure caused thereat. The flexible substrate itself tends to brake away from the panel due to its own cut or a crack of electrodes at terminal portion. Moreover, when the thickness of the transparent substrate becomes about 0.2 mm or less, the above-mentioned defects tend to occur in a high probability even under such stress caused by a step of general handling by workers. To deal with such problem, the connecting portion of transparent substrate and a flexible substrate would be coated with resin to reinforce that portion. However, there would be a problem that the manufacturability becomes low and thus requiring higher cost.
In order to try to avoid the above-mentioned problems, various methods are proposed. For example, a large-sized polarizing plate is coated on outer surface of an LC panel so as to extend outside of edges of the transparent substrate to protect the edge portions of the substrate, as disclosed in Japanese Utility-model application Laid-Open No. 60-94631 and Japanese Patent Publication No. 3799870.
On the other hand, in Japanese Patent Application Laid-Open No. 2005-338699, a pair of reinforcing tapes is used to sandwich a connecting portion of a flexible substrate and an LC panel. In Japanese Patent Application Laid-Open No. 2004-62048, a reinforcing tape is also used to cover the edge portion of an LC panel and bonded to a flexible substrate.
However, in the structure using a large-sized polarizing plate as disclosed in the above stated former two prior documents (No. 3799870 and No. 60-94631), there is no protective function for the flexible substrate, and thus cut and breakup of a flexible substrate cannot be prevented.
In the structure using a reinforcing tape as disclosed in the above stated latter two prior documents (No. 2005-338699 and No. 2004-62048), the width of the cited reinforcing tape is narrower than the flexible substrate, and thus cut and breakup of the flexible substrate cannot be prevented. This is because the reinforcing tape does not cover the whole part where transparent substrate is one, and thus breakage and lacking of transparent substrate cannot be prevented.